Extra-articular implantable mechanical energy absorbing systems and implantation method

ABSTRACT

A system and method for sharing and absorbing energy between body parts. In one aspect, the method involves identifying link pivot locations, fixing base components and minimally invasive insertion techniques. In one particular aspect, the system facilitates absorbing energy between members forming a joint such as between articulating bones.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a Divisional of, and claims priority under 35 U.S.C.§120 to, U.S. application Ser. No. 13/422,133, filed 16 Mar. 2012, whichis a Continuation of, and claims priority under 35 U.S.C. §120 to, U.S.application Ser. No. 12/690,687, filed 20 Jan. 2010, which is aContinuation of, and claims priority under 35 U.S.C. §120 to, U.S.application Ser. No. 11/775,149, filed 9 Jul. 2007, which is aContinuation-in-Part of, and claims priority under 35 U.S.C. 120 to,both of U.S. application Ser. No. 11/743,097, filed 1 May 2007, and Ser.No. 11/743,605, filed 2 May 2007, the entire disclosures of which areexpressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

The present invention is directed towards systems and methods fortreating tissue of a body and more particularly, towards approachesdesigned to reduce mechanical energy transferred between members forminga natural joint.

Both humans and other mammals belong to the subphylum known asvertebrata. The defining characteristic of a vertebrate is consideredthe backbone or spinal cord, a brain case, and an internal skeleton. Inbiology, the skeleton or skeletal system is the biological systemproviding physical support in living organisms. Skeletal systems arecommonly divided into three types—external (an exoskeleton), internal(an endoskeleton), and fluid based (a hydrostatic skeleton).

An internal skeletal system consists of rigid (or semi-rigid)structures, within the body, moved by the muscular system. If thestructures are mineralized or ossified, as they are in humans and othermammals, they are referred to as bones. Cartilage is another commoncomponent of skeletal systems, supporting and supplementing theskeleton. The human ear and nose are shaped by cartilage. Some organismshave a skeleton consisting entirely of cartilage and without anycalcified bones at all, for example sharks. The bones or other rigidstructures are connected by ligaments and connected to the muscularsystem via tendons.

A joint is the location at which two or more bones make contact. Theyare constructed to allow movement and provide mechanical support, andare classified structurally and functionally. Structural classificationis determined by how the bones connected to each other, while functionalclassification is determined by the degree of movement between thearticulating bones. In practice, there is significant overlap betweenthe two types of classifications.

There are three structural classifications of joints, namely fibrous orimmovable joints, cartilaginous joints and synovial joints.Fibrous/Immovable bones are connected by dense connective tissue,consisting mainly of collagen. The fibrous joints are further dividedinto three types:

-   -   sutures which are found between bones of the skull;    -   syndesmosis which are found between long bones of the body; and    -   gomphosis which is a joint between the root of a tooth and the        sockets in the maxilla or mandible.

Cartilaginous bones are connected entirely by cartilage (also known as“synchondroses”). Cartilaginous joints allow more movement between bonesthan a fibrous joint but less than the highly mobile synovial joint.Synovial joints have a space between the articulating bones for synovialfluid. This classification contains joints that are the most mobile ofthe three, and includes the knee and shoulder. These are furtherclassified into ball and socket joints, condyloid joints, saddle joints,hinge joints, pivot joints, and gliding joints.

Joints can also be classified functionally, by the degree of mobilitythey allow. Synarthrosis joints permit little or no mobility. They canbe categorized by how the two bones are joined together. That is,synchrondoses are joints where the two bones are connected by a piece ofcartilage. Synostoses are where two bones that are initially separatedeventually fuse together as a child approaches adulthood. By contrast,amphiarthrosis joints permit slight mobility. The two bone surfaces atthe joint are both covered in hyaline cartilage and joined by strands offibrocartilage. Most amphiarthrosis joints are cartilaginous.

Finally, diarthrosis joints permit a variety of movements (e.g. flexion,adduction, pronation). Only synovial joints are diarthrodial and theycan be divided into six classes: 1. ball and socket—such as the shoulderor the hip and femur; 2. hinge—such as the elbow; 3. pivot—such as theradius and ulna; 4. condyloidal (or ellipsoidal)—such as the wristbetween radius and carps, or knee; 5. saddle—such as the joint betweencarpal thumbs and metacarpals; and 6. gliding—such as between thecarpals.

Synovial joints (or diarthroses, or diarthroidal joints) are the mostcommon and most moveable type of joints in the body. As with all otherjoints in the body, synovial joints achieve movement at the point ofcontact of the articulating bones. Structural and functional differencesdistinguish the synovial joints from the two other types of joints inthe body, with the main structural difference being the existence of acavity between the articulating bones and the occupation of a fluid inthat cavity which aids movement. The whole of a diarthrosis is containedby a ligamentous sac, the joint capsule or articular capsule. Thesurfaces of the two bones at the joint are covered in cartilage. Thethickness of the cartilage varies with each joint, and sometimes may beof uneven thickness. Articular cartilage is multi-layered. A thinsuperficial layer provides a smooth surface for the two bones to slideagainst each other. Of all the layers, it has the highest concentrationof collagen and the lowest concentration of proteoglycans, making itvery resistant to shear stresses. Deeper than that is an intermediatelayer, which is mechanically designed to absorb shocks and distributethe load efficiently. The deepest layer is highly calcified, and anchorsthe articular cartilage to the bone. In joints where the two surfaces donot fit snugly together, a meniscus or multiple folds of fibro-cartilagewithin the joint correct the fit, ensuring stability and the optimaldistribution of load forces. The synovium is a membrane that covers allthe non-cartilaginous surfaces within the joint capsule. It secretessynovial fluid into the joint, which nourishes and lubricates thearticular cartilage. The synovium is separated from the capsule by alayer of cellular tissue that contains blood vessels and nerves.

Cartilage is a type of dense connective tissue and as shown above, itforms a critical part of the functionality of a body joint. It iscomposed of collagenous fibers and/or elastin fibers, and cells calledchondrocytes, all of which are embedded in a firm gel-like groundsubstance called the matrix. Articular cartilage is avascular (containsno blood vessels) and nutrients are diffused through the matrix.Cartilage serves several functions, including providing a framework uponwhich bone deposition can begin and supplying smooth surfaces for themovement of articulating bones. Cartilage is found in many places in thebody including the joints, the rib cage, the ear, the nose, thebronchial tubes and between intervertebral discs. There are three maintypes of cartilage: hyaline, elastic and fibrocartilage.

Chondrocytes are the only cells found in cartilage. They produce andmaintain the cartilaginous matrix. Experimental evidence indicates thatcells are sensitive to their mechanical (stress-strain) state, and reactdirectly to mechanical stimuli. The biosynthetic response ofchondrocytes was found to be sensitive to the frequency and amplitude ofloading (Wong et al., 1999 and Kurz et al., 2001). Recent experimentalstudies further indicate that excessive, repetitive loading may inducecell death, and cause morphological and cellular damage, as seen indegenerative joint disease (Lucchinetti et al., 2002 and Sauerland etal., 2003). Islam et al. (2002) found that continuous cyclic hydrostaticpressure (5 MPa, 1 Hz for 4 hours) induced apoptosis in humanchondrocytes derived from osteoarthritic cartilage in vitro. Incontrast, cyclic, physiological-like loading was found to trigger apartial recovery of morphological and ultra-structural aspects inosteoarthritic human articular chondrocytes (Nerucci et al., 1999).

Cancellous bone (also known as trabecular, or spongy) is a type ofosseous tissue which also forms an important aspect of a body joint.Cancellous bone has a low density and strength but very high surfacearea, that fills the inner cavity of long bones. The external layer ofcancellous bone contains red bone marrow where the production of bloodcellular components (known as hematopoiesis) takes place. Cancellousbone is also where most of the arteries and veins of bone organs arefound. The second type of osseous tissue is known as cortical bone,forming the hard outer layer of bone organs.

Various maladies can affect the joints, one of which is arthritis.Arthritis is a group of conditions where there is damage caused to thejoints of the body. Arthritis is the leading cause of disability inpeople over the age of 65.

There are many forms of arthritis, each of which has a different cause.Rheumatoid arthritis and psoriatic arthritis are autoimmune diseases inwhich the body is attacking itself. Septic arthritis is caused by jointinfection. Gouty arthritis is caused by deposition of uric acid crystalsin the joint that results in subsequent inflammation. The most commonform of arthritis, osteoarthritis is also known as degenerative jointdisease and occurs following trauma to the joint, following an infectionof the joint or simply as a result of aging.

Unfortunately, all arthritides feature pain. Patterns of pain differamong the arthritides and the location. Rheumatoid arthritis isgenerally worse in the morning; in the early stages, patients often donot have symptoms following their morning shower.

Osteoarthritis (OA, also known as degenerative arthritis or degenerativejoint disease, and sometimes referred to as “arthrosis” or“osteoarthrosis” or in more colloquial terms “wear and tear”), is acondition in which low-grade inflammation results in pain in the joints,caused by wearing of the cartilage that covers and acts as a cushioninside joints. As the bone surfaces become less well protected bycartilage, the patient experiences pain upon weight bearing, includingwalking and standing. Due to decreased movement because of the pain,regional muscles may atrophy, and ligaments may become more lax. OA isthe most common form of arthritis.

The main symptoms of osteoarthritis is chronic pain, causing loss ofmobility and often stiffness. “Pain” is generally described as a sharpache, or a burning sensation in the associated muscles and tendons. OAcan cause a crackling noise (called “crepitus”) when the affected jointis moved or touched, and patients may experience muscle spasm andcontractions in the tendons. Occasionally, the joints may also be filledwith fluid. Humid weather increases the pain in many patients.

OA commonly affects the hand, feet, spine, and the large weight-bearingjoints, such as the hips and knees, although in theory, any joint in thebody can be affected. As OA progresses, the affected joints appearlarger, are stiff and painful, and usually feel worse, the more they areused and loaded throughout the day, thus distinguishing it fromrheumatoid arthritis. With progression in OA, cartilage looses itsviscoelastic properties and it's ability to absorb load.

Generally speaking, the process of clinical detectable osteoarthritis isirreversible, and typical treatment consists of medication or otherinterventions that can reduce the pain of OA and thereby improve thefunction of the joint. According to an article entitled Surgicalapproaches for osteoarthritis by Klaus-Peter Günther, MD, over recentdecades, a variety of surgical procedures have been developed with theaim of decreasing or eliminating pain and improving function in patientswith advanced osteoarthritis (OA). The different approaches includepreservation or restoration of articular surfaces, total jointreplacement with artificial implants, and arthrodeses.

Arthrodeses are described as being reasonable alternatives for treatingOA of small hand and foot joints as well as degenerative disorders ofthe spine, but were deemed to be rarely indicated in largeweight-bearing joints such as the knee due to functional impairment ofgait, cosmetic problems and further side-effects. Total jointreplacement was characterized as an extremely effective treatment forsevere joint disease. Moreover, recently developed joint-preservingtreatment modalities were identified as having a potential to stimulatethe formation of a new articular surface in the future. However, it wasconcluded that such techniques do not presently predictably restore adurable articular surface to an osteoarthritic joint. Thus, thecorrection of mechanical abnormalities by osteotomy and jointdebridement are still considered as treatment options in many patients.Moreover, patients with limb malalignment, instability andintra-articular causes of mechanical dysfunction can benefit from anosteotomy to provide pain relief. The goal being the transfer ofweight-bearing forces from arthritic portions to healthier locations ofa joint.

Joint replacement is one of the most common and successful operations inmodern orthopaedic surgery. It consists of replacing painful, arthritic,worn or diseased parts of the joint with artificial surfaces shaped insuch a way as to allow joint movement. Such procedures are a last resorttreatment as they are highly invasive and require substantial periods ofrecovery. Joint replacement sometimes called total joint replacementindicating that all joint surfaces are replaced. This contrasts withhemiarthroplasty (half arthroplasty) in which only one bone's jointsurface is replaced and unincompartmental arthroplasty in which bothsurfaces of the knee, for example, are replaced but only on the inner orouter sides, not both. Thus, arthroplasty as a general term, is anoperative procedure of orthopaedic surgery performed, in which thearthritic or dysfunctional joint surface is replaced with somethingbetter or by remodeling or realigning the joint by osteotomy or someother procedure. These procedures are also characterized by relativelylong recovery times and their highly invasive procedures. The currentlyavailable therapies are not condro-protective. Previously, a popularform of arthroplasty was interpositional arthroplasty with interpositionof some other tissue like skin, muscle or tendon to keep inflammatorysurfaces apart or excisional arthroplasty in which the joint surface andbone was removed leaving scar tissue to fill in the gap. Other forms ofarthroplasty include resection(al) arthroplasty, resurfacingarthroplasty, mold arthroplasty, cup arthroplasty, silicone replacementarthroplasty, etc. Osteotomy to restore or modify joint congruity isalso an arthroplasty.

Osteotomy is a related surgical procedure involving cutting of bone toimprove alignment. The goal of osteotomy is to relieve pain byequalizing forces across the joint as well as increase the lifespan ofthe joint. This procedure is often used in younger, more active orheavier patients. High tibial osteotomy (HTO) is associated with adecrease in pain and improved function. However, HTO does not addressligamentous instability—only mechanical alignment. HTO is associatedwith good early results, but results deteriorate over time.

Other approaches to treating osteoarthritis involve an analysis of loadswhich exist at a joint. Both cartilage and bone are living tissues thatrespond and adapt to the loads they experience. If a joint surfaceremains unloaded for appreciable periods of time the cartilage tends tosoften and weaken. Further, as with most materials that experiencestructural loads, particularly cyclic structural loads, both bone andcartilage begin to show signs of failure at loads that are below theirultimate strength. However, cartilage and bone have some ability torepair themselves. There is also a level of load at which the skeletonwill fail catastrophically. Accordingly, it has been concluded that thetreatment of osteoarthritis and other conditions is severely hamperedwhen a surgeon is not able to precisely control and prescribe the levelsof joint load. Furthermore, bone healing research has shown that somemechanical stimulation can enhance the healing response and it is likelythat the optimum regime for a cartilage/bone graft or construct willinvolve different levels of load over time, e.g. during a particulartreatment schedule. Thus, there has been identified a need for deviceswhich facilitate the control of load on a joint undergoing treatment ortherapy, to thereby enable use of the joint within a healthy loadingzone.

Certain other approaches to treating osteoarthritis contemplate externaldevices such as braces or fixators which control the motion of the bonesat a joint or apply cross-loads at a joint to shift load from one sideof the joint to the other. Various of these approaches have had somesuccess in alleviating pain but suffer from patient compliance or lackan ability to facilitate and support the natural motion and function ofthe diseased joint. Notably, the motion of bones forming a joint can beas distinctive as a finger print, and thus, each individual has his orher own unique set of problems to address. Therefore, mechanicalapproaches to treating osteoarthritis have had limited applications.

Prior approaches to treating osteoarthritis have also been remiss inacknowledging all of the basic functions of the various structures of ajoint in combination with its unique movement. That is, in addition toaddressing loads at a joint and joint movement, there has not been anapproach which also acknowledges the dampening and energy absorptionfunctions of the anatomy, and taking a minimally invasive approach inimplementing solutions. Prior devices designed to reduce the loadtransferred by the natural joint typically describe rigid body systemsthat are incompressible. Mechanical energy is the product of force (F)and displacement distance (s) of a given mass (i.e., E=F×s, for a givenmass M). These systems have zero displacement within their working body(s=0). Since there is no displacement within the device it is reasonableto say that there is no energy storage or absorption in the device. Suchdevices act to transfer and not absorb energy from the joint. Bycontrast the natural joint is not a rigid body but is comprised ofelements of different compliance characteristics such as bone,cartilage, synovial fluid, muscles, tendons, ligaments, etc. asdescribed above. These dynamic elements act to both transfer and absorbenergy about the joint. For example cartilage compresses under appliedforce and therefore the resultant force displacement product representsthe energy absorbed by cartilage. In addition cartilage has a non linearforce displacement behavior and is considered viscoelastic. Such systemsnot only absorb and store, but additionally act to dissipate energy.

Therefore, what is needed and heretofore lacking in prior attempts totreat joint pain is an implantation method and implant device whichaddresses both joint movement and varying loads as well as dampeningforces and energy absorption provided by an articulate joint.

The present invention satisfies these and other needs.

SUMMARY OF THE INVENTION

Briefly and in general terms, the present invention is directed towardstreating diseased or mal-aligned body components. In one aspect, thepresent invention is embodied in methods and devices for treating andpreserving body joints.

In one approach to a method of device implantation, a pre-operativesession is performed to assess the need at a joint and to map thearticulation of the members forming the joint. Attachment sites are alsoassessed pre-operatively. During surgical intervention, a first rotationpoint location is identified along a first member of a joint. Next,access is gained to an area proximate the first pivot link location anda first base component is fixed upon the first member in a mannermaintaining use of the first rotation point location. A second rotationpoint location is then identified along a second member of a joint andsurgical access is obtained proximate the second rotation pointlocation. Subsequently, a second base component is fixed along thesecond member while maintaining use of the second rotation pointlocation. A subcutaneous channel is provided between the first andsecond rotation point locations and an energy manipulator is insertedwithin the channel. The energy manipulator is thereafter mounted to thebases. A tissue barrier is placed about the energy manipulator toprotect joint anatomy.

In a contemplated method, the energy manipulation assembly of thepresent invention can be initially configured to off-load or manipulateloads to a desired degree, and to be later altered as patient needs arebetter determined or change. Accordingly, post-operative alterations arecontemplated. In this regard, it is also contemplated there be noinitial off-loading or load manipulation until the interventional siteheals and the device is firmly implanted. Moreover, as needs change, themethod can involve removal or replacement of one or more components ofthe energy manipulation assembly. Further, various degrees ofnon-invasive approaches can be employed as is practical for a giveninterventional procedure.

In one aspect of treating and preserving body joints, the presentinvention is embodied in methods and devices implanted under thepatient's skin for relieving joint pain that do not require modificationof articular cartilage. In a preferred aspect, the device is implantedunder the patient's skin but outside of the joint capsule. In aparticular aspect, the joint pain is caused by osteoarthritis.

In one embodiment, the present invention addresses the pain associatedwith joint disease and mal-alignment. In presently contemplatedembodiments, a minimally invasive approach is taken to alleviate painwhile preserving full motion of the bones forming a joint. The devicesof the present invention accomplish one or more of: absorbing energyduring normal gait, reducing load on at least a portion of the naturaljoint, load transferring or bypassing, energy cushioning, and loadsharing or redistribution. In addition, both energy dampening and shockabsorption are considered in effecting such load manipulations. Further,the particular anatomy of a patient is considered in the contemplatedapproaches in that loads on desired portions of anatomy are manipulatedwithout overloading healthy surfaces. It is believed that employing theapproaches of the present invention can slow the progression of diseaseaffecting the joint and can further improve alignment, stability, orsupport or enhance medial collateral ligament (MCL) or lateralcollateral ligament (LCL) function.

In a preferred embodiment, the present invention adds an energy absorberto the joint to reduce energy transferred through the natural joint.

The present invention can be used unilaterally, bilaterally ormulti-laterally around a body joint.

The present invention has the capacity to absorb energy in addition totransfer energy from the joint. The simplest embodiment of the presentinvention incorporates a linear elastic spring. The energy absorption ofthe spring can be expressed as the product of force and displacement. Inaddition to a linear spring element, non linear spring members can beemployed to alter the energy absorption behavior under the same loadingor displacement conditions. Although actual springs are used to showvarious embodiments of the present invention, these elements could alsobe substituted with a material or other device with spring-likecharacteristics (e.g., an elastomeric member). Such elastomers includethermoplastic polyurethanes such as Tecoflex, Tecothane, Tecoplast,Carbothene, Chronthane and ChronoFlex (grades AR, C, AL). Moreover,materials such as Pebax, C-flex, Pellathane and silicone and siliconefoam can also be employed.

In other embodiments, spring systems may be coupled with dampeningdevices such as dash pots. In these embodiments, the spring element is astorage or absorber device while the dashpot acts to dissipate theenergy from the spring. Such embodiments alter the velocity ofdisplacement of the spring, thereby altering the energy absorptionbehavior. Although more traditional dampening devices are used to showvarious embodiments of the present invention, these elements could alsobe substituted with a material or other device with dampeningcharacteristics (e.g., a small pore sponge).

The operations of these embodiments and the prior art rigid systems canbe described graphically using force versus displacement diagrams (massis assumed constant). Thus a rigid body system that allows nodisplacement, no energy absorbed by the device, can be compared with asimple linear spring system of the present invention where energy isabsorbed in proportion to a spring constant (i.e., stiffness of thespring) as well to spring and dampener combination systems where theenergy absorbed is a function of the spring constant and the dampener.

One particular beneficial aspect of the energy absorption systems of thepresent invention are that they are capable of absorbing a constantamount of energy from the joint independent of joint kinematics orloading conditions. In contrast, the rigid body systems of the prior art(such as a cam system) are based on the physician separating (i.e.,distracting) the natural joint a given distance in the unloaded stateand attaching the rigid body system. The rigid body system thenmaintains this distance/distraction throughout the gait cycle andthrough bending of the joint. To maintain this distraction, the rigidbody must transfer a wide range of forces directly depending on jointkinematics.

Another particularly beneficial aspect of the energy absorption systemof the present invention is that the absorption system may be designedto absorb, dissipate and/or transfer energy at different rates orpositions in the gait cycle thereby enabling customization of the systemto the specific need. Considering the knee joint by way of example, if aspring system is coupled to a dampener to create a viscoelastic body,the system may be designed to absorb severe sudden impact loads (such asjumping) and dissipate these loads after the impact event. This mode ofoperation is akin to the natural role of cartilage. Conversely, thesystem can be designed to behave primarily as an energy transfer unitduring high rates of knee motion (e.g. sprinting/running) but act as anenergy absorber during normal rates of motion (e.g. walking).

Yet another particularly beneficial aspect of the energy absorptionsystem of the present invention is that the absorption system may alsobe tuned to occur at particular points in the gait or flexion cycledepending on the disease state. For example an individual withconcentrated loading at heel strike may only require absorption at thisphase of knee motion so the system may be adjusted to act only duringthis region of the gait cycle. Alternatively an individual may havefocal loss of cartilage on the posterior aspect of the femoral condyleand so stair climbing or kneeling becomes painful or problematic. Inthis scenario the system would be adjusted to absorb energy in thekinematic positions necessary and thereby maintaining the normal kneeenergy transfer outside of supporting the diseased locations.

In another beneficial aspect of the present invention, components of thesystem are designed for easy removal and, if necessary, replacementwhile others are intended for permanent fixation. The permanentcomponents are fixation base components which can have bony ingrowthpromoting surfaces and are responsible for fixation of the system to theskeletal structure. The removable components include the mobile elementsof the system such as the energy manipulation members and/or the pivotsor ball joints.

Various joints of the body can be treated employing the systems andmethods of the present invention. In particular, articulating bonesinvolved in synovial joints can benefit from the present invention.Accordingly, there are contemplated applications to the joints in theknee, ankle, shoulder, hip, hand and wrist. Further, the presentinvention can have applications in treating cartilaginous joints such asthose found in the spine.

In a further aspect, the present invention seeks to accomplish 1 to 40%energy or load reduction while maintaining full motion of the bodyparts. A 5 to 20% energy or load reduction has been postulated to bedesirable in certain circumstances to accomplish the alleviation of painwithout approaching undesirable load shielding. The devices of thepresent invention further provide greater energy manipulation duringjunctures of highest loads placed between body parts as well as lessenergy manipulation when loads between members decrease. In this way,the present invention complements the action of body parts such as thosefound at joints.

In some joints, it is desirable that 100% of the energy be absorbed bythe device(s), such joints may be those in the hands or upper extremity.In such cases, it may be desirable to have the devices placedbilaterally on either side of the joint. In the lower extremity, insevere cases, 100% energy absorption is achievable, however this mayexpose the device to more wear and shorter life. Some patients mayaccept this if the device is able to bridge the patient through adifficult period and it is easily replaced or removed without impactingthe patients ability to receive a total joint replacement later.

In another embodiment of the present invention, an energy absorptiondevice is implanted at a diseased joint to restore cyclic,physiological-like loading thereby protecting chondrocytes from loadinduced apoptosis.

In yet another embodiment of the present invention, an energy absorptiondevice is implanted at a diseased joint to facilitate at least a partialrecovery of morphological and ultra-structural aspects in osteoarthriticarticular chondrocytes.

In another embodiment of the present invention, an energy absorptiondevice is implanted adjunctively with a cartilage repair procedure suchas mosaicplasty, osteochondral allograft transfer, autologouschondrocyte implantation or microfracture. Such an adjunctive procedurewould enable less strict rehabilitation regimes while simultaneouslyprotecting the graft and stimulating it with appropriate motion.

In another embodiment of the present invention, an energy absorptiondevice is implanted in conjunction with a uni-compartmental jointreplacement prosthesis or total joint replacement prosthesis. Suchcombination procedure will reduce wear rates by reducing the loads andcontact forces between surfaces of the joint prosthesis.

Rotation point location of the energy manipulation member on the femuris determined in part by the mechanism of the device. The inventors ofthe present invention have discovered regions on the femoral chondyl inwhich a rotation point on the device relative to a tibial rotation pointalong a line normal to the ground from the femoral rotation point willeither have minimal displacement, lengthening of the device orshortening of the device as the joint moves from full extension toflexion. Therefore, if the desired device is to function by elongationits rotation point will be located in the appropriate region.Conversely, if the desired device is to function by compression itsrotation point will be located in a different appropriate region.

In one specific embodiment, the present invention is embodied in adevice utilizing an element, or elements functioning as a unit, whichresponds to bending or changes in elongation. In an application to aknee joint, this device forms a bending spring that is to span thetibiofemoral joint and be anchored into the tibia and femur. Further,the device is used to take on some of the loading experienced by thearticular surfaces of the tibiofemoral joint, thus unloading the joint.In one embodiment, the device is designed to off load the joint duringknee extension. Unloading in this phase is governed by the compressionof the device—increased compression yields increased joint un-loading.The device is anchored in a position which ensures device elongationresulting from knee flexion. As the knee moves into flexion, the deviceis un-compressed and will cause little to no joint off-loading. Thedevice may have other features which ensure correct device alignment,and prevent against buckling, as the device transitions into acompressed state. The device can also be configured to provideoff-loading during flexion.

In another specific approach, the present invention is embodied in a camengagement assembly utilizing contacting elements, at least one of whichhaving an eccentric contacting surface. The element, or elements,possessing the eccentric surface define a cam. Again in an applicationto the knee joint, one element is anchored to the femur and the other tothe tibia. Implanted, the device will span the tibiofemoral joint. Thedegree, duration, and instance of elemental contact is dictated by theprofile of the cam element or elements. In one embodiment, the cam isdesigned to cause increased contact stress between the device elementswhich span the joint when the knee is in extension. During instances ofincreased contact stress, the normal energy experienced by the articularsurfaces of the tibiofemoral joint will be absorbed and taken on, inpart, by the device. During instances of knee flexion, the cam profilewill ensure little or no engagement leading to joint off-loading. Thus,the amount of energy absorption will be controlled by a spring elementwhich backs the cam element. The spring element can be adjusted, orexchanged, to tune the amount of energy absorption across the joint.

In yet another specific approach, a segmented support assembly isemployed to address joint needs. This concept utilizes multiple elementsthat align to provide columnar support at desired phases of kneemovement. In one application, the device is designed to provide columnarsupport during phases of knee extension. That is, each element isconstrained by the adjacent element in a variable fashion—leastconstrained during states of elongation and most constrained duringstates of compression. The variable motion constraint, or tolerancewhich increases with elongation, is designed so that the cumulativeeffect is to accommodate the complex motion of the tibiofemoral jointfor example as it transitions from extension into flexion. The device isanchored, via mounting components, in a way that dictates deviceelongation during knee flexion and device compression during kneeextension. During the state of device compression, the device willexperience part of the energy normally taken on by the articularsurfaces of the tibiofemoral joint—thus reducing the energy absorbed bythe joint by a desired amount. The amount of energy absorption can beadjusted, via the mounting components, to a desired and measurableamount. The assembly will accommodate the transition from an unloaded toa loaded state by the use of elements, possessing either spring ordampening characteristics, either in the device mounting components orin between the mating surfaces of the device elements.

In a further approach, the invention is embodied in a piston supportassembly. This approach employs a spring loaded piston mechanism toabsorb energy normally experienced by the anatomical joint. The pistonis comprised of an axially mobile member or rod moving in a definedpath. Depending on the axial position of the rod, a compressible springis engaged thereby transferring load through the mechanism. When thespring is not engaged no absorbing or load transfer occurs. The devicemay utilize rigid and coaxial elements that ride into or through eachother. Load transfer and energy absorption occurs when the spring isengaged. For this system to function without hindering the range ofmotion of the knee for example, the fixation or attachment pointsbetween bone and piston mechanism are free to revolve about an axis(possibly multiple axes). In addition, the piston is capable of rotatingabout its longitudinal axis to facilitate rotational along the axis ofthe anatomical joint.

The present invention also includes a staged procedure. In this aspect,the energy absorption system is comprised of permanent fixation basecomponents and removable energy absorption. The permanent fixation basecomponents incorporate a bone ingrowth promoter on their bone contactingsurface (e.g. porous surface, calcium phosphate coating, texturedsurface etc.). It is important to stimulate this interface usingmoderate loads to ensure the creation of a bony interface, howeveroverloading the interface prematurely may prevent bone ingrowth. Tofacilitate bony ingrowth, it is possible that the system will beimplanted in a mode of operation whereby it is absorbing small amountsof load to create a moderate load condition at the interface. Asubsequent simple procedure will be completed at an appropriate timepost implantation to adjust the energy absorption settings to absorbhigher amounts of load.

In one particular aspect, three dimensional (3D) navigation is employedto accomplish placement of a peri-articular joint. The joint in questionis scanned with natural or added landmarks thereat using CT, MRI orother remote imaging techniques. This data is imputted into a 3Dnavigational software and tracker system. Tracker technology couldemploy RF, optical or electromagnetic imaging. Further, the tracker canbe self-powered or it may be passive. In combination with a referencetool, the tracker then facilitates accurate placement of an energymanipulating system across the target joint.

The present invention also contemplates intra-articular drug delivery incombination with joint energy and load manipulation. In one contemplatedapproach, a drug release device is loaded with a drug and a sustainedreleased drug carrier, and placed at a target area within or near adiseased or malaligned joint, such as on or in the device of the presentinvention. Various drugs and mechanisms for sustained release are alsocontemplated.

Moreover, in certain aspects, the present invention also contemplatesemploying sensors to provide information on performance. For example,pressure sensors can be placed within or adjacent the device or anatomyto indicate aspects of function and loads. Sensors in the implant mayallow for non-invasive telemetry and capture of information regardingjoint motion. Telemetry may be usable to control various settings in thedevice.

The present invention also contemplates that the components arecompatible with joint diagnostic techniques such as magnetic resonanceimaging and computed tomography.

Additionally, the present invention contemplates post-operativepercutaneous adjustability and tuning of the implant's characteristicsin response to patient feedback. It may be desirable to detect theinternal tension and/or dampening setting of the device while it isbeing accessed percutaneously or alternatively have those featureseasily detectable using x-ray or another non-invasive modality such asultrasound.

In one contemplated approach, a core shaft of the energy manipulationassembly can be ribbed like a ratchet about which is configured amoveable piston mounted on a collar equipped with a pair of spacedbuttons. Depression of the buttons cause complementary structure oninside of the collar to become disengaged from the ribs of the coreshaft so that adjustments can be made. The assembly can be furtherconfigured so that the adjustment can be made only when the joint is inflexion and only when both buttons are deliberately pressed.

Another aspect of some embodiments of the present invention is toenclose at least a part of the energy manipulating device in a sheath.The sheath allows the tendons and soft tissue to avoid being abraded bythe presence of the implant in that region during movement. By allowingthe tissue to form a capsule around the sheath of the implant, thetissue will be strengthened and the likelihood of erosion will bereduced. The sheath also allows for easy replaceability, in someembodiments, of the link components because they can be inserted intothe sheath once the original components are removed without causing anyadditional tissue disruption.

The present invention also contemplates, a method of locating areference point on a side of a femur and a corresponding referencelocation on a side of a tibia of a knee joint such that the referencepoint and reference location are at a defined distance apart as the kneejoint moves from 0° flexion to at least 60° flexion. In one approach,the reference point and reference location move further apart as theknee joint moves from 0° flexion to at least 60° flexion. In anothermodification, the base components are attached to the femur and tibiaand an energy manipulation member is attached to the base componentssuch that their respective rotation attachment points are aligned withthe corresponding reference point and reference location.

Other features and advantages of the present invention will becomeapparent from the following detailed description, taken in conjunctionwith the accompanying drawings, which illustrate, by way of example, theprinciples of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view, depicting the normal forces existing in a joint;

FIG. 2 is a front view, depicting the present invention incorporatedinto the joint shown in FIG. 1;

FIG. 3 is a front view, depicting the effect an energy manipulatingassembly of the present invention has on the joint shown in FIGS. 1 and2;

FIG. 4 is a graph, illustrating the energy characteristics of a priorart rigid structure applied across a joint;

FIG. 5 is a graph, illustrating the energy characteristics of a linearspring system of the present invention;

FIG. 6 is a graph, illustrating the energy characteristics of a springand dampening system of the present invention; and

FIG. 7 is a graph, illustrating the flexion/extension angle and jointforce existing in a gait cycle;

FIG. 8 is a graph, illustrating one approach to energy absorption on agait cycle;

FIG. 9 is a graph, illustrating a second approach to energy absorptionon a gait cycle;

FIG. 10 is a graph, illustrating a third approach to energy absorptionon a gait cycle;

FIG. 11 is a graph, illustrating a fourth approach to energy absorptionon a gait cycle;

FIG. 12 is a perspective view, depicting anatomy of a typical kneejoint;

FIG. 13 is a perspective view, depicting proximal and distal basecomponents mounted at a joint;

FIG. 14 is a perspective view, depicting the base components of FIG. 13with an energy manipulation assembly attached therebetween;

FIG. 15 is a perspective view partially in cross-section, depicting onepreferred embodiment of an energy manipulation;

FIG. 16 is a perspective view, depicting the assembly of FIG. 15including a tissue barrier;

FIG. 17A is an elevation view; depicting a first step in an implantationprocedure;

FIG. 17B is a perspective view, depicting a second step in animplantation procedure;

FIG. 18 is a diagrammatic view, depicting motion patterns and selectedfixation points for energy manipulation devices;

FIG. 19 is a perspective view, depicting a third step in an implantationprocedure;

FIG. 20 is an elevation view, depicting positioning of a proximal basecomponent in an implantation site;

FIG. 21 is an elevation view, depicting yet a further step in animplantation procedure;

FIG. 22 is a perspective view, depicting yet still a furtherimplantation procedure step;

FIG. 23 is a perspective view, depicting the formation of a secondaccess hole of the implantation procedure;

FIG. 24 is an elevation view, depicting a completely implanted energymanipulation device;

FIG. 25A is a partial cross-sectional view, depicting one embodiment ofadjustment sub-structure;

FIG. 25B is a partial cross-sectional view, depicting another embodimentof adjustment sub-structure;

FIG. 25C is an enlarged view, depicting an adjustment ring of FIG. 25Bshown in a ratchet engaged state;

FIG. 25D is an enlarged view, depicting the adjustment ring of FIG. 25Cin a ratchet release state;

FIG. 26A is a side view, depicting an energy manipulation assembly ofthe present invention;

FIG. 26B is a side view, depicting the assembly of FIG. 26A afterarticulation of body members;

FIG. 27 is a front view, depicting a bi-lateral (or lateral and medial)application of a lower manipulation assembly of the present invention;

FIG. 28 is a side view, depicting a bending spring energy manipulationassembly of the present invention;

FIG. 29 is a side view, depicting the assembly of FIG. 28 afterarticulation of body members;

FIG. 30 is a front view, depicting the energy manipulation assembly ofFIG. 28;

FIG. 31 is a side view, depicting a energy manipulation assemblyincluding a pair of springs;

FIG. 32 is a side view, depicting the assembly of FIG. 31 afterarticulation of body members;

FIG. 33 is a perspective view, depicting a bending spring energymanipulation assembly including a guide shaft;

FIG. 34 is a side view, depicting a energy manipulation assemblyincluding locking structure;

FIG. 35 is a side view, depicting an energy absorbing spring assemblyincluding undulations configured along a helical path;

FIG. 36 is a perspective view, depicting a energy manipulation assemblyincluding load bearing members and a central spring;

FIG. 37 is a perspective view, depicting another embodiment of a bendingspring assembly with a midsection spring;

FIG. 38 is a front view, depicting yet another energy manipulationassembly including a central spring;

FIG. 39 is a perspective view, depicting a yet further bending springassembly with a central spring;

FIG. 40 is a perspective view, depicting a bending spring assemblyincluding a stop member;

FIG. 41 is a perspective view, depicting the bending spring assembly ofFIG. 40 in its compressed configuration;

FIG. 42 is a perspective view, depicting adjustable attachment structureof a energy manipulation assembly;

FIG. 43 is a partial cross-sectional view, depicting dampening structureof an attachment assembly;

FIG. 44 is a perspective view, depicting another embodiment of anattachment structure of a load bearing member;

FIG. 45 is a cross-sectional view, depicting mounting structure formedin body anatomy;

FIG. 46 is a partial cross-sectional view, depicting a energymanipulation assembly affixed to the body anatomy shown in FIG. 45;

FIG. 47 is a cross-sectional view, depicting a load bearing assemblycontained substantially entirely within body anatomy;

FIG. 48 is a side view, depicting an enlarged view of the energymanipulation assembly shown in FIG. 47;

FIG. 49 is a side view, depicting a bending spring energy manipulationassembly including a slot for articulating movement;

FIG. 50 is a side view, depicting another embodiment of a bending springassembly including pivoting structure;

FIG. 51 is a side view, depicting yet a further embodiment of a bendingspring assembly including pivoting structure;

FIG. 52 is a perspective view, depicting a energy manipulation assemblyincorporating cam engagement structure;

FIG. 53 is a side view, depicting the load bearing assembly shown inFIG. 52;

FIG. 54 is a perspective view, depicting yet another embodiment of aenergy manipulation assembly;

FIG. 55 is a perspective view, depicting a energy manipulation assemblyincluding multiple camming surfaces;

FIG. 56 is a front view, depicting a energy manipulation assemblyincluding camming surfaces and spring biasing structure;

FIG. 57 is a perspective view, depicting yet another embodiment of aenergy manipulation assembly including multiple camming surfaces;

FIG. 58 is a front view, depicting a energy manipulation assemblyincluding camming surfaces and pivoting substructure;

FIG. 59 is a partial cross-sectional view, depicting a ball bearing incombination with camming surfaces;

FIG. 60 is a side view, depicting a energy manipulation assemblyemploying a ball-like camming surface;

FIG. 61 is a side view, depicting the assembly of FIG. 60 in relation toarticulated body members;

FIG. 62 is a front view, depicting a energy manipulation assemblyincorporating segmented support substructure;

FIG. 63 is a side view, depicting the assembly shown in FIG. 62 furtherincorporating a slotted engagement arrangement;

FIG. 64 is a perspective view, depicting another embodiment of asegmented support subassembly;

FIG. 65 is a perspective view, depicting yet another embodiment of asegmented support subassembly;

FIG. 66 is a perspective view, depicting yet still another segmentedsupport subassembly;

FIG. 67 is a side view, depicting members forming a segmented supportsubassembly;

FIG. 68 is a perspective view, depicting disengaged members of asegmented support subassembly;

FIG. 69 is a perspective view, depicting a segmented support assemblyencased in an outer sheath;

FIG. 70 is a perspective view, depicting both a longitudinally arrangedsegmented support assembly and its configuration upon bending;

FIG. 71 is a perspective view, depicting a segmented support assemblyincluding variable interlocking links in combination with springassemblies;

FIG. 72 is a side view, depicting yet another embodiment of a segmentedenergy manipulation assembly;

FIG. 73 is a side view, depicting still yet another embodiment of asegmented energy manipulation assembly;

FIG. 74 is a partial cross-sectional side view, depicting still yetanother segmented support assembly for a energy manipulation assembly;

FIG. 75 is a partial cross-sectional view, depicting the assembly ofFIG. 74;

FIG. 76 is a bottom view, depicting the assembly shown in FIG. 74;

FIG. 77 is a side view, depicting a segmented energy manipulationassembly including slotted attachment structure;

FIG. 78 is a side view, depicting a modification to the assembly shownin FIG. 77;

FIG. 79 is a front view, depicting a energy manipulation assemblyincorporating segmented and articulating structure;

FIG. 80 is a side view, depicting sheathing of members of a energymanipulation assembly;

FIG. 81 is a perspective view, depicting further aspects of a segmentedsupport assembly of the present invention;

FIG. 82 is a side view, depicting yet further aspects of segmentedsupport assemblies of the present invention;

FIG. 83 is a side view, depicting a energy manipulation assemblyincluding articulating and segmented structure;

FIG. 84 is a front view, depicting a energy manipulation assemblyincorporating piston support;

FIG. 85 is a side view, depicting the assembly of FIG. 84 afterarticulation of body members;

FIG. 86 is a front view, depicting another embodiment of a energymanipulation assembly incorporating piston support;

FIG. 87 is a cross-sectional view, depicting substructure of theassembly shown in FIG. 86;

FIG. 88 is a partial cross-sectional view, depicting another embodimentof a piston support subassembly;

FIG. 89 is a partial cross-sectional view, depicting yet anotherembodiment of a piston support subassembly;

FIG. 90 is a perspective view, depicting still yet another embodiment ofa piston support subassembly;

FIG. 91 is a perspective view, depicting the assembly of FIG. 90 in acompressed configuration;

FIG. 92 is a perspective view, depicting a further embodiment of aenergy manipulation assembly incorporating piston support structure;

FIG. 93 is a perspective view, depicting a telescoping arrangement of apiston support subassembly;

FIG. 94 is a perspective view, depicting the assembly of FIG. 69 in acompressed configuration;

FIG. 95 is a cross-sectional view, depicting a energy manipulationassembly substantially completely imbedded within body tissue;

FIG. 96 is a cross-sectional view, depicting another approach to aenergy manipulation assembly substantially completely imbedded withinbody tissue;

FIG. 97 is a cross-sectional view, depicting a first step in theimplantation of a energy manipulation assembly incorporating pistonsupport;

FIG. 98 is a cross-sectional view, depicting a second step in theimplantation of the assembly shown in FIG. 97;

FIG. 99 is a perspective view, depicting a load bearing member of aenergy manipulation assembly including piston support and incorporatingrotational substructure;

FIG. 100 is a perspective view, depicting adjustment substructure of aenergy manipulation assembly for the present invention;

FIG. 101 is a cross-sectional view, depicting further aspects of theassembly depicted in FIG. 100;

FIG. 102 is a perspective view, depicting further aspects which can beincorporated into the assembly depicted in FIG. 100;

FIG. 103 is a perspective view, depicting adjustment structure of aenergy manipulation assembly of the present invention;

FIG. 104 is a cross-sectional view, depicting a first step in theimplantation of a sheathed energy manipulation assembly;

FIG. 105 is a cross-sectional view, depicting a second step in animplantation approach of the assembly depicted in FIG. 80;

FIG. 106 is a cross-sectional view, depicting the assembly of FIG. 105fully implanted;

FIG. 107 is a cross-sectional view, depicting an enlarged view of animplanted energy manipulation assembly including piston support;

FIG. 108 is a cross-sectional view, depicting an alternate embodiment ofa energy manipulation assembly incorporating piston support implantedwithin body anatomy;

FIG. 109 is a cross-sectional view, depicting further substructure whichmay be incorporated into the assembly depicted in FIG. 108;

FIG. 110 is a cross-sectional view, depicting another embodiment of aenergy manipulation assembly of the present invention incorporatingpiston support substructure;

FIG. 111 is a perspective view, depicting a energy manipulation assemblyincluding lateral substructure spanning a width of treated body tissue;

FIG. 112 is an enlarged view, depicting substructure of the devicedepicted in FIG. 111;

FIG. 113 is an enlarged view, depicting substructure of the devicedepicted in FIG. 111;

FIG. 114 is a cross-sectional front view, depicting the assembly of FIG.111;

FIG. 115 is a cross-sectional view, depicting yet another component ofthe assembly depicting in FIG. 111;

FIG. 116 is a perspective view, depicting a further embodiment of aenergy manipulation assembly incorporating piston support;

FIG. 117 is a cross-sectional view, depicting substructure of theassembly depicted in FIG. 116;

FIG. 118 is a cross-sectional view, depicting other substructure of theassembly depicted in FIG. 116;

FIG. 119 is a back view, depicting yet another approach for an energymanipulation assembly;

FIG. 120 is a perspective view, depicting the approach shown in FIG.119;

FIG. 121 is a side view, depicting a further embodiment of an energymanipulation assembly of the present invention;

FIG. 122 is a perspective view, depicting a bilateral approach of thepresent invention;

FIG. 123 is a perspective view, depicting another bilateral approach ofthe present invention;

FIG. 124 is a perspective view, depicting an embodiment of the presentinvention where the body anatomy is aligned;

FIG. 125 is a perspective view, depicting the embodiment of FIG. 124with the body anatomy in an articulated configuration;

FIG. 126 is a perspective view, depicting an embodiment of the presentinvention incorporating pivoting and disengaging structure;

FIG. 127 is a perspective view, depicting the embodiment of FIG. 126with the anatomy in an articulated position;

FIG. 128 is a perspective view, depicting yet another embodiment ofmounting structures attached to body anatomy;

FIG. 129 is a perspective view, depicting still yet another embodimentof mounting structure attached to body anatomy;

FIG. 130 is a perspective view, depicting yet another approach to anenergy manipulation assembly;

FIG. 131 is an isometric view, depicting another energy manipulationassembly of the present invention.

FIG. 132 is a perspective view partially in cross-section, depictingstill yet another embodiment of the present invention;

FIG. 133 is a perspective view, depicting the application of the presentinvention to another body joint;

FIG. 134 is an enlarged view, depicting the energy manipulation assemblyof FIG. 132;

FIG. 135 is a side view, depicting the application of the presentinvention to a foot joint;

FIG. 136 is a top view, depicting the application of the presentinvention to a finger joint;

FIG. 137 is a side view, depicting an alternate to the approach shown inFIG. 135;

FIG. 138 is a perspective view, depicting the application of the presentinvention to a spinal joint; and

FIG. 139 is a perspective view, depicting another application of thepresent invention to a spinal joint.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, which are provided by way of example andnot limitation, the present invention is directed towards apparatus andmethods for treating body tissues. In applications relating to thetreatment of body joints, the present invention seeks to alleviate painassociated with the function of diseased or malaligned members forming abody joint. Whereas the present invention is particularly suited toaddress issues associated with osteoarthritis, the energy manipulationaccomplished by the present invention lends itself well to broaderapplications. Moreover, the present invention is particularly suited totreating synovial joints such as the knee and shoulder. However, it isalso contemplated that the apparatus and method of the present inventioncan be employed to treat the spine facet joints and spine vertebraljoints as well as other synovial and various other joints of the bodysuch as those of the hand and feet.

In one particular aspect, the present invention seeks to permit andcomplement the unique articulating motion of the members defining a bodyjoint of a patient while simultaneously manipulating energy beingexperienced by both cartilage and osseous tissue (cancellous andcortical bone). Approaches involving varying energy absorption andtransfer during the pivoting of the joint and selecting a geometry forthe energy absorption assembly to provide necessary flexibility areimplemented into various embodiments of the present invention. Certainof the embodiments include geometry which accomplishes variable energyabsorption designed to minimize and complement the dampening effect andenergy absorption provided by the anatomy of the body, such as thatfound at a body joint. It has been postulated that to minimize pain,off-loading or absorption of 1-40% of forces, in varying degrees, may benecessary. Variable off-loading or absorption in the range of 5-20% canbe a target for certain applications. In certain specific applications,distraction is employed in the energy manipulation approach.

Conventional or surgical or minimally invasive approaches are taken togain access to a body joint or other anatomy requiring attention.Arthroscopic approaches are thus contemplated when reasonable to bothimplant the energy manipulation assembly as well as to accomplishadjusting an implanted assembly. Moreover, biologically inert materialsof various kinds can be employed in constructing the energy manipulationassemblies of the present invention.

In one particular approach, a bending spring assembly is contemplated tomanipulate or absorb forces between body parts. Thus, an assemblyutilizing an element or elements which respond to bending or changes inelongation may be desirable to treat afflictions such as osteoarthritis.Certain of the assemblies can incorporate features which insure correctdevice alignment and prevent against buckling as the member transitionsbetween compressed and uncompressed states.

Turning now to FIGS. 1-3, the forces occurring between body joints isdiscussed. The arrows of FIG. 1 depict the forces occurring betweenadjacent members of a body joint lacking an energy manipulation assemblyof the present invention. However, in body anatomy incorporating thepresent invention, less forces are transferred to the bones andcartilage of the members defining the joint. Where the body joint istreated with the foregoing described energy manipulating assemblies ofthe present invention, a degree of the forces between body members isabsorbed by the energy manipulating assembly (depicted as arrows 54).Accordingly, less force 56 is placed on natural body anatomy.

FIGS. 4-6 depicts the relation between force (F) and displacement (S)between members of a body joint (where mass is constant). In a rigidbody system (FIG. 4) which does not incorporate aspects of the presentinvention, there is no displacement and no energy absorption. In anenergy manipulating system incorporating a single linear spring (FIG.5), energy is absorbed in proportion to a spring constant (springstiffness). The energy absorbed is represented by the shaded area 59below the curve. As shown in FIG. 6, where a spring and dampener is usedin combination, the energy absorbed 59 is a function of the springconstant and the dampener. It is these relationships which areconsidered in developing desired energy manipulating characteristics.

Also considered are the forces existing through the flexion andextension through an articulation cycle of anatomy to be treated. Usingthe gait cycle of the legs of a human as an example, both the jointforce and flexion/extension angle in degrees can be plotted versus thepercentage of the gait cycle completed. A normal or expectedrelationship 60 of vertical forces generated through the gait cycle isdepicted in each of FIGS. 7-11. Also depicted in the FIGS. is theflexion/extension angle 62. The expected relationship 60 of verticalforces during the gait cycle can be altered using certain of theembodiments of the energy manipulation assemblies of the presentinvention. As shown in FIG. 118, the energy manipulation assemblies canabsorb energy by a fixed proportion during a portion of the gait cycle.This is reflected by curve 64. Moreover, energy can be both absorbed anddampened as represented by curve 66 of FIG. 9 or alternatively, energycan be absorbed only above a fixed value as represented by curve 68 ofFIG. 10. Additionally, as reflected by curve 70 of FIG. 11, energy canbe absorbed in a fixed range of motion. It is to be recognized, however,that each of or one or more of these types of energy absorption can becombined in a desired system.

Referring now to FIG. 12, the medial side anatomy of a typical kneejoint is presented in a manner relating to an implantation procedure.Such a procedure could ultimately involve the implantation of devicessuch as those described below. Although the knee joint is beingdescribed here, it is contemplated these devices can also be placed atother joints throughout the body.

In a procedure seeking to off-load or manipulate forces at a knee joint,a proximal attachment site (DAS) for a base component of an energymanipulation device must be identified. Similarly, a distal attachmentsite (PAS) must also be selected. In a contemplated approach the medialproximal attachment site (PAS) can be located on a femur in a spacebounded by the medial patellar retinaculum (MPR), the vastus medialis(VM) and the tibial collateral ligament (TCL). The distal attachmentsite (DAS) can be located on the tibia in a space between the medicalpatellar retinaculum (MPR) and the pes anserinus (PA).

Turning now to FIG. 13, there is shown proximal 72 and distal 73 basecomponents positioned upon first 74 and second 75 members, respectivelyof a typical body joint. Here, the terminal end portions of the femurand tibia are depicted without surrounding tissue. It is noted that thebase components 72 and 73 are contoured to match potential mountingsurfaces of the femur and tibia. FIG. 14 further shows one embodiment ofan energy manipulation device 76 configured between and mounted to thebase components 72, 73.

One preferred embodiment of an energy manipulation system 77 is shown inFIGS. 15 and 16. This system includes a proximal base anchor 78 attachedto a proximal base component 72 and a distal base anchor 79 attached toa distal base component 73. Articulation surfaces 81 are furtherprovided at a junction between the base anchors 78, 79 and the basecomponents 72, 73. Articulation surfaces 81 allow multiple degrees offreedom between the base anchors and energy absorber assembly 82.Configured between the base anchors 78, 79 is an energy absorberassembly 82 including energy absorbing sub-structure such as a spring,configured within a stabilizer, here shown as sliding sleeves 83. Withparticular reference to FIG. 16, the system 77 can further include asubcutaneous tissue barrier in the form of a sheath 84, preferablyePTFE, which encloses various parts of the system and excludessurrounding tissue. It is contemplated that the subcutaneous tissuebarrier can be formed from or coated alternatively with a tissuein-growth substance or for that matter, substances which inhibit suchin-growth. For example, it may be desirable that one or more sides orportions of the energy manipulation system 77 enclosed by the sheath 84be affixed to surrounding tissue whereas it may be advantageous thatother portions of the system be free to move with respect to surroundingtissue. The energy manipulation system 77 itself would be left to moverelative to the sheath 84.

With reference now to FIGS. 17-24, aspects of a contemplatedimplantation approach are described. With the anatomy of the knee jointin mind, a pre-operative session with the patient is conducted. Byemploying two-dimensional or three dimensional static or motion imagingtechniques which are available, such as x-ray, MRI or CT scans, theanatomy of the interventional site is examined. A dynamic assessment canbe performed to map the articulating motion of the members defining theparticular joint.

The data collected during the pre-operative session is logged and thencompared to data sets developed by the physician and/or the organizationutilized to store actual patient data as well as tested theoretical dataindependently developed. Easily accessible and convenient to useprograms or charts can be developed and employed to automate thecomparison of a particular patient's condition with previously collecteddata. From this comparison, a specific treatment modality is selectedfor the patient. Moreover, an expected device selection or multipledevice selections are made from the various devices contemplated totreat the patient.

The pre-operative session or an intra-operative session further includesthe collection of three-dimensional information concerning an expectedproximal attachment site (PAS) and a distal attachment site (DAS). Thislends itself to the selection of the proper base components.

Once the surgical intervention date is set and as it approaches, thepatient's health is continued to be closely monitored. On the day of theprocedure, the patient is prepared for surgery in the conventionalmanner. In a particular application, spinal anesthesia or generalanesthesia can be used as a step to prepare the patient.

Next, the knee or other joint being treated is imaged using fluoroscopy(See FIG. 17) or along with three-dimensional navigational software suchas that available from Striker or Brainlab. The members defining thejoint are placed in a full lateral position and perpendicularly to thereceiver of the imaging device. The proximal joint member is then fixedusing a vacuum splint/sandbag (not shown) or similarly effective device.In a preferred procedure to treat the knee joint, the Blumensaat's line85 of the femur bone 86 is used as a landmark for locating the variouscomponents of an energy manipulation device as it has been found toprovide a convenient initial position marker for ultimately achievingproper rotational positioning of the device. Other referencing pointscan additionally be used and of course are required when treating otherjoints.

Accordingly, it is further contemplated that other regions can representpossible locations of a femoral rotation point or reference point on themedial chondyle. In order to select such an alternative point, thesurface area of the medial chondyle is mapped to determine regionscorresponding to changes in device length of a potentially implantedenergy manipulation assembly while the joint is moved from fullextension to full flexion. Areas of device increasing length anddecreasing length are mapped. Moreover, areas are also identified wherethere is an initial device length increase then followed by a lengthdecrease, and where there is an initial length decrease followed byincreasing length. Mapping of areas of overlap between these variousareas represent transitions from one region to a next. An arearepresenting minimal displacement is also identified. This informationis then employed to identify the various points of rotation best suitedfor a particular energy manipulation implant. As length change iscontemplated to be insensitive to a tibial rotation point or referencelocation, the tibia point therefore remains fixed.

Furthermore, an approach to proper implant placement can involveobserving changes in device length at 90° flexion relative to a fullyextended length. These length changes are measured relative to a femoralrotation point at a midpoint of the Blumensaat's line shown in fulllateral view of the medial side. The device and rotation point is thenselected based upon desired measurement changes. The tibial rotationpoint is then identified by selecting a point directly inferior to thefemur rotation point.

In at least the first described approach, a circle guide is then placedover the joint with the center thereof configured at a midpoint of theBlumensaat's line (FIGS. 17A and 17B). As shown in FIG. 18, it has beenfound that when considering device elongation and compression, alongwith anterior and posterior device positioning as well as flexiondegrees during a patient's gait, that +/−5 mm from a center point of aBlumensaat's line can be a starting reference point. At this point, itis confirmed that the tibial plateau at 90° flexion is 1-2 rings outsideof an initial matching circle at 0° flexion, if the device selected forthe patient is only meant to extend during flexion. At a mid-point ofthe Blumensaat's line and perpendicularly thereto, the physician willthen insert a rigid guide or K-wire 87 through a center guide hole 88 ofthe circle guide 86 that has been previously locked in place. The K-wire87 includes a sharp terminal tip for entering bone and thus the K-wire87 can either be drilled into the bone or tapped in by force. After theK-wire 87 has been fixed perpendicularly to the bone, the circle guide86 is removed and the K-wire is shortened leaving approximately one inchof wire protruding through the skin. A proximal base component mounthole is then configured over the K-wire placed adjacent the leg toestimate proper placement while using remote image techniques.

With specific reference to FIGS. 19 and 20, an incision 89 is madesuperior to the K-wire 87. Fascia and tissue are then manipulated toexpose bone periostium in the region of anticipated base componentattachment. The periostium is next displaced to promoteosteointegration. The proximal base component 72 is inserted within theincision 89 and a mounting hole of the proximal base component 72 isplaced over the K-wire 87. In order to do so, the skin will requireretracting beyond and away from the K-wire 87 to place the mounting hole90 of the proximal base component 72 over the K-wire 87. The proximalbase component 72 is then positioned to optimize fit and bone screws 91are employed to fix the base component 72 to the bone. An intermediatestep can include loosely attaching the base component 72 prior tocompletely turning down the bone screws 91 so that a most advantageouslyplacement is achieved. It is to be further recognized that variousangles of insertion of the bone screws 91 can be used to aid inproviding attachment support in a multitude of directions. Moreover,bicortical penetration of the bone screws is contemplated for certainapplications.

In one approach, it is contemplated that bicortical screws can bepolyaxial because their trajectory will be fixed by the bicorticalpurchase. Their trajectories can either diverge or converge by about 15to 30 degrees to improve pull out strength but the exact angle isprobably not important so the technique can be simplified by lettingthem rotate in a small cone. Further, the unicortical screws can havefixed trajectories. This will increase their stability that they maylack because of the unicortical purchase. The trajectories should eitherconverge or diverge as above but the angles will be set. Moreover, it iscontemplated that none of the screws “lock” to the plate via a secondset of threads. This may reduce the ability to generate compressionbetween the bone and the porous coatings and as there may be a need toreduce/eliminate as many gaps as possible. It may further be desirableto use a resorbable bone void filler under the plate to eliminate gapsand prevent ingrowth of fibrous tissues. This might also provide someleeway when the plate shapes are not exact. Finally, an anti back-outfeature is contemplated for the screws in certain applications.

Turning now to FIGS. 21-24, the location and fixation of a distal basecomponent 73 is described. With the joint members, here the femur andtibia, placed in a fully extended position, a vertical line is takendown from the mounting hole 90 of the proximal base component 72 to adistance approximately 45 mm-55 mm along the tibia. The circle guide 86can again be used to aid in this step. Alternatively, as shown in FIG.21, a tibial guide cross-bar device 92 can be placed to engage theK-wire 87 at one end and using remote imaging, arranged so that a guidecross bar thereof is perpendicular to a top of the tibial surface. Thelocation of the distal base component 73 is then estimated both visuallyon the outside of the skin as well as remotely such as by usingfluoroscopy or other techniques.

The skin is then incised 93 along the distal joint member or in thepresent application, along the tibia. Alternatively, the first incisioncan be used to access the distal joint member via a subcutaneouschannel. In this regard, one long incision can alternatively be usedextending across the joint members. Also, a single small incision can bemade at the center of the joint or on either side of a joint from whicha tunnel is formed to access a target site on either side of the joint.The fascia and tissue in the area is manipulated to expose boneperiostium in the target region and the bone is displaced to againpromote bone in-growth into a subsequently placed distal base component73. The distal base component 73 is then positioned to optimize fit andbone screws 91 are inserted to affix the component to the bone. Again,prior to completely turning the screws to fix the base component,further adjustment is contemplated.

Subsequent to forming a subcutaneous channel between the basecomponents, the energy absorber sub-assembly 76 of the energymanipulation device is then attached to the base components 72, 73.Although various embodiments of the energy manipulation device arecontemplated, in general, the device will include replaceable andadjustable proximal and distal articulate structure (e.g., ball andsocket joints, U-joints/limbs) attached to the base components 72, 73 aswell as a replaceable and adjustable mid-section accomplishing theenergy manipulation. A sheath is further provided about these structuresto protect the surrounding tissue. The sheath can form part of thissub-assembly or be added later. In attaching such structure to the basecomponents 72, 73, the members defining the joint are placed in fullflexion in order to minimize spring force.

Once the energy manipulation device is completely implanted, theincisions are closed and allowed to heal. Subsequent post-operativesteps are taken to verify proper placement and to accomplish anynecessary adjustment. In this regard, two or three-dimensional states ofmotion image techniques can be used to observe effectiveness. That is,in one approach, it is desired that the spring or other energymanipulation sub-structure be compressed 80-90% at full extension of thejoint members. It also may be desired to configure the implant so thatno loads are initially placed thereon. Once it is determined that theimplant has completely attached to the bone and the area has healed, itis then adjusted to achieve load manipulation. Multiple subsequentadjustments or component replacement are also contemplated as well aspercutaneous approaches to the same.

In an alternative related approach to implantation, a scan of the targetjoint is performed. Natural or added landmarks can be employed duringthe scanning step for orientation purposes and the patient's need areaccessed and documented. The data extracted during the scanningprocedure is then imported into a three dimensional (3D) navigationalsoftware and associated tracker. The tracker can employ RF, optical, orelectromagnetic energies and can be self-powered or be passivelypowered. A guidewire delivery tool is then attached to the tracker.Software is activated to automatically manipulate the tracker into adesired position relative to the landmarks. A reference tool is thenimported to the area for guidewire delivery on bases proximal and distalto a target joint. Next, orientation of a guidewire trajectory point isperformed based upon pre-calculated ideal points as determined bydesired functional needs of the periarticular joint.

Once guidewires are placed on the members defining the joint, a properbase component can be selected based upon three dimensional datagathered concerning the anatomy of the target joint. After gainingaccess to the bones and completing other preliminary steps describedabove, the base components can be fixed to the bones employing screws orthe like. Thereafter, rotation points are attached to the basecomponents and the tracker is again employed to perform fine adjustmentsas to fine tune locations of the structures. Finally, the energymanipulation substructure is placed between and connected to therotation point assemblies.

The fact that the implant will be relatively superficial presents theopportunity to allow interaction with it through the skin withoutpuncture. The concept is that the height of the piston (or other energymanipulation structure) engagement would be adjustable by squeezing thedevice on either side when the device is completely unloaded (flexedposition). It is contemplated that a core shaft of an implant can beribbed like a ratchet, and the movable piston (or other sub-structure)is mounted on a collar that has two relative large “buttons” on eitherside. Depression of the buttons causes the teeth on the inside of thecollar to disengage when the device is completely unloaded. Compressionon only one button does not release either of the teeth—only bothbuttons releases the teeth. Further, due to the morphology of the teethand the ratchet, the assembly can be arranged so that even depression ofboth teeth when the device is loaded will not release the collar. Thus,inadvertent release during loading could not occur. Every time thecollar is moved up or down while the buttons are being depressed in theunloaded position there can be an audible click. Accordingly, withoutx-ray the doctor can adjust the device in the office and a table can beprovided for the significance of the clicks with respect to un-loading.Firm finger pressure on the device in the unloaded position would beenough to disengage the collar and relocate it to a new position. Localanesthetic on the skin and a pincher tool can be used while employingfluoroscopy to find the buttons, depress them and relocate the housingto a new position.

Turning now to FIGS. 25A-D, there is shown approaches to adjusting anenergy absorber assembly. In the approaches depicted, the assembliesinclude a ratchet core 94 including outwardly projecting and angledteeth. A spring-biased collar piston assembly 95 is further provided andconfigured in a lockable arrangement with the ratchet core 94. In afirst approach (FIG. 25A), the collar/piston assembly 95 is furtherprovided with spring biased button 96 (here shown biased in a closedposition by an elastomeric ring) having a distant terminal end. As thebuttons are each depressed inwardly, this engagement with the teeth ofthe ratchet core disengages, thereby allowing the assembly 95 to move upor down. As the assembly 95 is so translated an audible sound is madebetween the detents of the buttons and the ratchet core 94.

In a second approach (See FIGS. 25B-D), the spring-biased collar/pistonassembly 95 is equipped with a two piece collar spring 97 which canassume both ratchet engaged (FIG. 25C) and ratchet released (FIG. 25D)configurations. Thus, by pressing on the spring arms 98 of thisembodiment of the spring-biased collar/piston assembly 95, the collardisengages from the ratchet core 94 and is permitted to be translatedlongitudinally. As a safety measure, it is to be appreciated that theangle and length of the teeth formed on the ratchet core 94 andcorresponding engaging structures of the collar assemblies can beconfigured to only allow translation if two points of the collar aresufficiently pressed.

As shown in FIGS. 26A and B, one embodiment of a bending spring assembly100 can be configured along members forming a body joint 102. Thebending spring assembly 100 includes one or more attachment structures104, 106 and a energy absorbing member 108. The attachment structures104, 106 are anchored to the members or bones forming the body joint102. The energy absorbing member 108 is in the form of a bending springand is attached to each of the attachment structures 104, 106. While themembers defining the joint 102 are generally longitudinally arranged,the energy absorbing member 108 absorbs and/or transfers forces beingbared by the members of the joint. In a simplified approach, the energyabsorbing member 108 can also apply lateral forces to the member of thejoint 102 during flexion.

As shown in FIGS. 26A and B, a bending spring assembly can be affixed toeither a lateral or medial side of a body joint 102. Furthermore, asdepicted in FIG. 27, and as well as with each of the disclosedembodiments, bending spring assemblies can additionally be placed onboth lateral and medial (or bilateral) surfaces of a body joint 102.Moreover, the energy manipulation achieved by a system of a plurality ofbending spring assemblies 100 can be configured to provide differentenergy manipulation on opposing sides of a joint 100 to therebyaccomplish a more complex energy absorption curve and where desiredvariable off-loading, while permitting and complementing the unique pathof motion of the members of a joint of a particular patient.

One particular approach to providing variable energy manipulation whilecomplementing the unique motion of members defining a joint is depictedin FIGS. 28-30. A energy absorbing assembly including an undulatingspring member 110 having a variable path can be attached to membersdefining a body joint 102. The variability of the path is selected toprovide additional dampening and/or energy absorption to thus off-loadone or more of the cartilage or osseous bones of the joint. Moreover,the energy absorbing spring assembly 110 can be configured to providesuch energy manipulation during extension and to become less activeduring flexion of the members of a joint 102.

Turning now to FIGS. 31 and 32, there is shown another approach toenergy manipulation employing a bending spring approach. Here, thebending spring assembly 112 includes a pair of springs attached on thesame side of a body joint 102. In this approach, the springs can provideenergy manipulation in both flexion and in extension. As shown in FIG.31, the compressed spring provides central off-loading in a directionnormal to joint structure and the extended spring is uncompressed so asto not distract a posterior section of the joint. When the members ofthe joint are in flexion (FIG. 32), the posterior spring provides energymanipulation normal to the direction of the lateral member of the jointwhile the centrally located spring provides no off-loading. Othercombinations of bend spring assemblies 112 are further contemplated toaccomplish other energy manipulation scenarios which may be useful inminimizing joint pain.

Further specific geometries of bending spring assemblies are depicted inFIGS. 33-41. Each of these devices contemplate approaches to energymanipulation which complement the unique motion of a joint of aparticular patient. In a first embodiment, the bending spring assembly114 includes a helical spring 116 configured about a guiding member 118.The helical spring 116 is further configured between anchor points 120which are affixed to a patient's anatomy. As the members defining a bodyjoint articulate, the anchor points 120 move with respect to each other,the guiding member 118 providing a controlled path for the spring 116and the spring 116 thereby provides the desired energy absorption and/orload transfer.

As shown in FIG. 34, a helical spring 122 of a bending spring assemblycan include interlocking structure 124 which alters the function of thespring 122. For example, the interlocking structure can be adapted toprevent rotation of the spring 122 at a predetermined amount ofcompression or extension of the spring 122. Thus, a variable energymanipulation can be provided by this structure. Moreover, such structurecan alternatively or additionally be employed to prevent or controljoint rotation at a given degree of extension or flexion.

A spring assembly 126 having an overall helical configuration isdepicted in FIG. 35. This spring assembly 126 further includesundulations 128 configured along the general helical framework as wellas sections with varying thickness. In these ways, the spring assembly126 can provide a varying energy absorption profile which matches theneeds of a particular body joint, providing energy manipulation duringcertain pre-determined phases of articulation of members defining thejoint. Similarly, a spring assembly can include spring portions dividedby a center section including an elastomeric sleeve (not shown) whichprovides the device with desired energy manipulation characteristics.Moreover, the elastomeric sleeve can be used in affixing the assembly atthe joint requiring treatment.

In related approaches (FIGS. 36-38), a mid-section of the bending springassembly includes a spring member 136. Opposing ends of the assemblyinclude bone anchors 138. As shown, the opposing ends can include one ormore attachment structures or bone anchors 138. Configured between thebone anchor structure 138 and on opposing sides of the central spring136 are load transfer beams 140. By way of a pivot configured betweenthe bone anchors 140 and beams 140, the load transfer beams 140 can bemade to rotate with respect to the bone anchors 138 and each other.

The bending spring assembly 142 depicted in FIG. 39 also includes acentrally located spring 144 configured between a pair of load transferbeams 146. As with previous embodiments, the spring 144 can assumevarious profiles characterized by varying widths and pitches to therebyprovide the desired energy manipulation profile.

FIGS. 40 and 41 depict yet another embodiment of a bending springassembly 148. In this embodiment, the energy is absorbed initially by anundulating beam 150. Upon near complete compression of the beam 150,curved portions thereof engage a centrally located stop member 152. Thestop member 152 can be formed of rigid or non-rigid material dependingon the energy manipulation that is desired in the application at hand.

Referring now to FIGS. 42-44, there are shown various details associatedwith attachment or mounting structure of a bending spring assembly, butthe assembly can be employed across all contemplated approaches. A rod154 connected to one such bending spring assembly (not shown) can becoupled to a bracket assembly 156 which is affixed to body anatomy of apatient. By way of an adjustment screw 157, the placement of the rod 154can be adjusted with respect to the bracket assembly 156. It iscontemplated that a needle screw (not shown) could be employed toaccomplish the necessary adjustment percutaneously. The bracket assembly156 can further or alternatively include a spring 158 (FIG. 43), thetension of which can be adjusted percutaneously to provide desireddampening or shock absorption at the ends of a bending spring assembly.Moreover, the bracket assembly 156 for any of the disclosed embodimentscan further include a textured surface 160 adapted for attachment topatient anatomy. Such texturing can be surface irregularities or cancome in the form of materials adapted for tissue in-growth.

Furthermore, the bending spring assemblies and for that matter each ofthe disclosed embodiments of energy manipulation assemblies, can beattached to body anatomy in various ways. As shown above, the assembliesof the present invention can be surface mounted upon anatomy byemploying anchors. Also, mounting structure 162 can be insertedcompletely or partially within bones 163, for example, such as that inthe manner depicted in FIGS. 21 and 22. Further anchoring of theassemblies can occur through a surface of the bone (See FIG. 46).Moreover, as shown in FIGS. 47 and 48, a energy manipulation assembly164 can be placed substantially entirely with a bone 163, leaving aterminal end thereof to accomplish desired energy transfer and/orabsorption.

The bending spring assemblies can embody rather complex structures. Asshown in FIG. 49, one contemplated bend spring assembly 166 including aspring 168 can be attached to a pair of spaced attachment structures170, 172. Such attachment structures 170, 172 can be directly connectedto body anatomy or can be further attached to structure mounted on orwithin anatomy. The spring 168 includes one end which is fixed orrotatably connected to a first attachment structure 170 and a second endis constrained within a curved slot formed in the second attachmentstructure 172. Again, this unique design is contemplated to provide abody joint or other anatomy with a desired energy absorption and/ortransfer profile which complements the unique articulation at the targettissue.

The spring 168 of a bending spring assembly 166 can likewise beconfigured between one ore more pivoting attachment structures 170, 172(See FIGS. 50, 51). In a first approach, as shown in FIG. 50, one orboth of the attachment structures 170, 172 are allowed to pivot about apivot point. The pivoting action of the attachment structures 170, 172of the device of FIG. 51 are constrained by stops 174.

Each of the previously and for that matter, hereinafter disclosedembodiments can incorporate or cooperate with sensing mechanisms adaptedto provide loading information concerning the tissues being treated.Thus, it is contemplated that the various pressured sensing mechanismsavailable can be placed upon the devices of the present invention. Suchsensors can be configured to provide information about the efficacy ofthe energy manipulating device of the present invention and whetheradjustments are necessary. Similarly, sensors can be placed on anatomyto provide information regarding loads being placed on the tissuesthemselves.

Furthermore, it is contemplated that drugs can be delivered to theinterventional site targeted for energy manipulation. In this regard,the entirety of the subject matter disclosed in U.S. Publication No.2007/0053963 is hereby incorporated by reference.

In other aspects, the present invention is embodied in a cam engagementassembly for energy manipulation. In this approach, the cam engagementassembly employs contacting elements, at least one of which has aneccentric contracting surface. The degree, duration and instance ofelemental contact is controlled by the profile of the cam element orelements. Increased contact stress is contemplated between deviceelements when the body anatomy members are in extension. During flexion,the cam profile can be configured to ensure little or no engagement. Theassembly can include a spring assembly that can be made to be adjusted,or exchanged, to tune the amount of energy absorption across anatomy.

Moreover, the surface engagement of the device can be created throughmultiple methods and can include such structure as wear-resistantbearing surfaces, ball bearings at a surface engagement site or a gearedengagement. The mounting features of the device can be contained inseparate mounting elements or incorporated into anatomy spring elements.The mounting design can further accommodate complex motion of a joint asit transitions from extension to flexion by allowing for rotation andpivoting, or through the use of compressible materials.

Various approaches to cam related energy manipulation are depicted inFIGS. 52-61. In a first embodiment (FIGS. 52 and 53), curved loadbearing surfaces 202 are configured to rotate with respect to eachother. The load bearing surfaces 202 are connected to attachmentstructure 204, 206 which in turn are affixed to body anatomy such asbones forming a joint. The connections between the load bearing surfaces202 and attachment structures 204, 206 or between the attachmentstructures 204, 206 and the bone can be spring loaded or otherwise becomprised of flexible or elastic materials. As the body anatomytransitions between extension (FIG. 28) and flexion (FIG. 29), theenergy bearing surfaces 202 move between varying degrees of engagement.In one aspect, it is contemplated that the greatest off-loading andenergy manipulation occurs between loading members 202 when the bodyanatomy is in its extension configuration. The varying degrees ofengagement are pre-selected to absorb energy between body members withthe aim of reducing or eliminating pain. In this way, unique paths ofmotion can be preserved during an attempt at absorbing energy.

Another embodiment of a cam engagement assembly is shown in FIG. 54. Inthis approach, a center load bearing, joint section 208 is configuredbetween a pair of spaced attachment brackets 210. Post members 212provide rotation points to define an articulating engagement assembly.Various connecting points 214 can be further provided along theattachment bracket 210 to receive the post members 212 to therebyprovide a means to readjust the assembly to fit a patient's needs. It isfurther contemplated that gearing structure (gears or gears and a rack)can be implemented into this embodiment to provide desired controlbetween moving parts.

Another embodiment of a cam engagement assembly 215 of the presentinvention is depicted in FIGS. 55 and 56. In this approach, cammingsurfaces 216 are adapted to fit the natural contour of the body anatomy.In one aspect, the camming surfaces 216 are provided along substantiallyan entire range of surfaces of natural tissue which may come intocontact. This structure is supplemented with a energy absorbing assembly218 comprising springs or other structure for absorbing energy fromareas of contact between the camming surfaces 216. Such an assembly 215is affixed at a joint or other body anatomy employing approachesdescribed herein.

Turning to FIG. 57, there is shown a cam engagement assembly 220including a first concave camming surface 222 and a second convexcamming surface 224. These surfaces are biased apart by a pair ofsprings 226 arranged in a parallel fashion. Each of the camming surfaces222, 224 include cavities for receiving a portion of the springs 226.The springs 226 act as a energy absorbing structure and in combinationwith the convex and concave surfaces 222, 224 complements the action ofthe body parts to which the assembly is attached.

A similar combination of elements is disclosed in FIG. 58. Here, thecamming surface assemblies 230 are at least at one end attached in aspring loaded arrangement 233 to brackets 232. A second camming surface230 can be connected in a manner to allow pivoting between the cammingsurface 230 assembly and bracket 232 such as by providing a slottedconnector 236. The brackets 232 are in turn affixed to body anatomy.Configured between the camming surface assemblies 230 is a load bearingspring assembly 238 which at opposing ends engages receiving holesformed in the camming surface assemblies 230.

As shown in FIG. 59, a ball bearing 240 can be strategically placedbetween camming surfaces 230 of a cam engagement assembly for thepurpose of aiding the relative motion between the structures. Such anapproach can be further incorporated into any of the disclosedassemblies. In one particular embodiment (FIGS. 60 and 61), a ballbearing 240 is placed between the anatomy of articulating members of apatient. Alternatively, a disc can be employed in like fashion. Ineither approach, the ball bearing structure 240 is supported by energyabsorbing springs 242 which are in turn attached to attachment structure246 mounted to patient anatomy.

A further aspect of the present invention is embodied in a segmentedsupport assembly. Generally, this approach employs multiple elementsthat align and mate to provide column support as desired, such as duringextension of loading parts. Thus, in one aspect, adjacent elementsforming a segmented support assembly can be constrained by an adjacentelement in a variable fashion to accommodate the complex motion ofarticulating members. The amount of energy manipulation is adjusted bymounting or attaching components via spring or dampening assemblies.

With reference to FIGS. 62 and 63, there is shown one embodiment of asegmented support assembly 300. Fixation base components 302 areprovided to attach the assembly to patient anatomy. Medially positionedpivot points 304 in combination with adjustable spacers 306 define asegmented load bearing member and provide desired off-loading as well asmulti-dimensional flexibility permitting the patient anatomy toarticulate freely. Being adjustable, the spacers 306 function tofacilitate alignment. In one particular aspect, at least one fixationcomponent 302 can include a slotted receiving trough 306 sized toreceive one terminal end 308 of the segmented load bearing member, theterminal end 308 slideably engaging the slot.

The segmented load bearing member can assume various shapes and forms.These approaches incorporate multiple, mating elements which providecolumnar support while facilitating multi-dimensional movement. Suchapproaches are shown in FIGS. 64-69. As depicted in FIG. 64, disc-likemembers 310 are connected in a series via interconnecting structures 312contemplated to permit three-dimensional translation between adjacentlyarranged discs 310. While three-dimensional motion is contemplated, thedegree of motion is constrained by the members defining the segmentedload bearing member. Accordingly, there can be limited axial compressionof the members so that there is a desired amount of columnar support.Likewise, lateral pivoting of the members is limited by the geometry ofthe adjacent discs. The lateral pivoting can be selected to permit andcomplement the unique articulation of a particular patient's anatomy.

The structure defining a segmented load bearing member can assumerelatively complex geometry. That is, various embodiments ofinterlocking links 314 can form a segmented load bearing member 316 (SeeFIGS. 65-70). Such links 314 can be held within a sheath 318 (FIGS. 65and 69) or can be locked together to permit articulation without theneed for an outer sheath (FIGS. 66-68 and 70). In a further aspect (SeeFIG. 70 for example), certain designs of the links 314 can include aprojection 320, a number of which are received within a variable shapedslot 322 of an adjacent link. The variable staged slot 322 can furtherinclude a narrower section 324 which is sized and shaped to engage theprojection 320 in a manner to both absorb loads as well as constrainarticulating motion.

Furthermore, as shown in FIG. 71, the links 314 of a segmented sectionof a load bearing member 316 can embody variably shaped links 314. Thatis, the geometry of the links 314 can vary along a length of a loadbearing member 316 to thereby provide differing articulation at variouspoints. Moreover, the assembly can incorporate one or more springs 326designed to facilitate desired energy absorption and/or dampening.

Other examples of assemblies including segmented load sharing linkagesin combination with spring assemblies are shown in FIGS. 72-76. In eachof these embodiments, springs 326 can be placed at one or more ends ofthe segmented load bearing members 316. It may be convenient toconfigure the springs 320 within attachment structures 302 employed toanchor the assembly to body anatomy. Springs 320 can also be placedalong other portions of the assembly to achieve desired effects.

In yet another embodiment (FIGS. 77 and 78), the assembly is providedwith slotted structure 330 rather than springs. The slotted structure330 can be configured within the attachment structure 302 and be bothgenerally vertical (FIG. 77) or generally horizontal (FIG. 78). Anadjustment screw 332 or similar structure can further be provided topermit adjustment of the attachment structure relative to patientanatomy and to the segmented load bearing structure 316.

Other of segmented support assemblies of the present invention employarticulating linkages rather than interlocking links to provide desiredresults (See FIGS. 79-83). The various contemplated articulate linkages334 can have a myriad of shapes and sizes and can include one or morepoints of articulation 336. Opposed ends of the linkages 334 are affixedto body anatomy in varying ways as well. As with all of the disclosedembodiments, mounting structure of one approach can be substituted foranother and thus, the load bearing assemblies can be surface mounted toanatomy or partially buried therewithin. Moreover, the linkages can besheathed (See FIG. 80) or can lack sheathing.

In yet another specific approach, the present invention employs pistonsupport to accomplish desired load manipulation. In general, theseembodiments include an axially mobile member which translates in adefined linear path. A compressible spring can be included to facilitateenergy absorption and transfer and the assembly can further includestructure permitting articulation between the piston subassembly and thebody anatomy.

A simplified approach involving a piston support, load manipulationassembly 400 is depicted in FIGS. 84 and 85. In this embodiment, thepiston member 402 is highly laterally flexible but also sufficientlylongitudinally rigid to thereby both bend with the articulation of bodymembers as well as absorb compression forces when the body members arein extension. One or more cylinders 404 are configured to acceptlongitudinal translation of the piston 402.

A piston support assembly 400 can further include springs 406 to aid inthe load manipulation being sought (See FIGS. 86 and 87). Such springs406 can be placed within an attachment cylinder 404 (FIG. 87) or can beadditionally or alternatively placed about the piston assembly 402.Moreover, the piston assembly 402 can assume a complex geometry whichincludes both pivot points 408 and/or curvilinear portions 410. As inall of the disclosed embodiments, the structure can be affixed to bodyanatomy so that it spans a joint between articulating members.

Further embodiments of piston-based load bearing members are disclosedin FIGS. 88-94. FIG. 88 discloses an arrangement when a spring 406 spansthe length of the piston member 402 and within spaced cylinders 404.FIG. 89 employs a piston member 402 which additionally includes bendingspring structures for energy manipulation. FIGS. 90 and 91 depict apiston assembly 402 including a knurled outer surface and is furthercontemplated to include means for adjusting the strength of its loadingcapabilities by rotating the piston with respect to the cylinder. FIG.92 shows an assembly which includes a spring 406 configured about thepiston 402 having a stepped profile and between a cylinder 404 and apair of stops 412. This assembly is also contemplated to be adjustablebetween high and low spring tensions.

A piston support based assembly 400 can also include a plurality oftelescoping members 414 arranged longitudinally. Thus, certain of thecircumferentially arranged telescoping members act both as pistons andcylinders for adjacent structure. By varying the energy which adjacenttelescopic members 414 can bear, a desired energy absorbing profile canbe provided by the structure to thereby absorb energy in a desiredsequence.

As previously described, the energy absorbing assemblies of the presentinvention can be surface mounted upon anatomy or can be insertedcompletely or partially within the target tissue. As shown in FIGS. 95and 96, a piston based, energy manipulation assembly 400 having one ormore cylinders 404 receiving a piston 402 can be substantiallycompletely implanted within a member defining a target tissue. Theportions extending out from a surface of the tissue provide the energyabsorbing characteristics needed for a particular application. Theassemblies 400 can also be configured to span articulating body membersand include a portion of the cylinder 404 being buried within bodytissue as shown in FIGS. 97 and 98.

Structure which is believed to be particularly suited for the situationsdepicted in FIGS. 97 and 98 is shown in FIG. 99. Here, the energyabsorbing assembly 402 includes a mid-section characterized by a pistonhaving bending spring qualities and further includes collars 416 whichare configured to rotate with respect to the piston. The collars 416 arealso sized and shaped to be placed into a reciprocating motion with acylinder.

With reference to FIGS. 100 and 101, the collars 416 can further includea washer and bearing arrangement which permits rotation of the collar416 and the piston or end 402. Further, a screw assembly can be employedto connect the mid-section of the piston assembly with the collar 416. Aspring 422 can be further provided within the collar 416 (See FIG. 101)to accept loads. The assembly 400 is then threaded within an attachmentstructure 424 and affixed to or within body tissue.

In a further modification to the approach in FIGS. 100 and 101, it iscontemplated that inner 430 and outer members 432 of the collar assembly416 can be adjustable post-implant. In a first embodiment (FIG. 102),the collar assembly 416 can include a percutaneously accessibleadjustment screw 434 which controls the relative positions between theinner and outer members 430, 432. One or more of the inner and outerhousings 430, 432 can alternatively be equipped with a gear surface 436that is accessible by a percutaneous gear shaft tool 438 (FIG. 103). Thetool 438 includes a terminal end 440 configured with a gear surfacecomplementary to that of the gear surface formed on the collar assembly416. In this way, tension as well as spacing of the components of aenergy manipulation assembly can be altered or corrected as needed.

A sheathed energy manipulation assembly 440 incorporating variousaspects of the present invention is shown in FIGS. 104-108. In thisembodiment, ends of the assembly are reciprocally mounted within bodytissue. The length of the device is encased in a sheath 442. It is to berecognized that various of the contemplated energy manipulationassemblies can be encased to thereby provide smooth surfaces which areless traumatic to body tissue. Moreover, as shown in the figures, one ormore spring assemblies 444 can be placed about and in apposition withload bearing structure.

As best seen in FIGS. 108 and 109, the piston-type bearing assembly canfurther include an adjustment screw 450 arranged in a parallel fashionwith respect to other energy absorbing structure to alter the effect ofthe same. Again, it is anticipated that such adjustment structure can beaccessed percutaneously after the load bearing assembly is placed at orwithin a target tissue.

Yet another embodiment of the present invention is disclosed in FIG.110. In this assembly, a pair of spaced attachment assemblies 460include projections 462 for engaging the tissue to be treated. Theattachment assemblies 460 further each include locking side screws 464as well as a rotatable access screw head 465 which operate to affect alongitudinal position (advancement and retraction) of a threaded shaftwith a ball-tipped terminal end. Configured between the longitudinallyspaced shafts 466 is a piston and cylinder assembly 468 having opposedends 470 with a socket sized to receive the ball portion of the threadedshaft 466. A first spring 472 is contained within the cylinder 474 ofthe assembly. A second spring 476 is coaxially arranged about thethreaded shafts 466 and piston and cylinder assembly 468. Further, asheath 477 is placed about these subassemblies from one attachmentassembly to another 460. Thus, this embodiment of a energy manipulationassembly provides both energy absorption as well as multi-dimensionaltranslation to permit body anatomy articulation.

Yet further details of useful energy manipulation are disclosed in FIGS.111-118. A bi-lateral energy manipulation assembly 480 includes a pairof laterally configured shafts 482, at the terminal ends of which areconnected a single energy absorbing member 484. The energy absorbingmember 484 can include a piston and spring assembly arranged and theshafts can extend a full width and length of the tissue being treated.Further, the laterally configured shafts 482 can include alongitudinally extending trough 486 employed to selectively engagecomplementary surfaces of the energy absorbing member assemblies 484.Also, as best seen in FIG. 112, tissue inserts 488 in the form ofcollars are contemplated to receive at least a portion of a length ofthe shafts 482. Such inserts 488 as well as other surfaces of thevarious disclosed embodiments and approaches can include a bone-ingrowthcoating or texture.

A related unilateral mounted device is shown in FIG. 116. In thisapproach, the shafts 482 extend less than a full width of the bodyanatomy but otherwise include a piston-based energy manipulationassembly 484. Once again, the members defining the piston assembly 484can be sheathed with encasing structure 486 and can pivot about endpoints 488. The encasing structure 486 can be applied to variousstructures of the disclosed embodiments and can be formed from PTFE,ePTFE, Dacron, Polypropylene, Polyethylene, or woven materials such assilk. This structure 486 can also be created from bioabsorbable materialand can be drug loaded or impregnated with silver or other agentscapable of stimulation or reducing inflammation. The piston subassemblycan further include a biasing spring 490 configured about a piston 492and placed in a position with an internal cylindrical sleeve 494. Withinthe internal cylindrical sleeve 494 can be configured a further energyabsorbing structure 496 such as a simple bending, columnar spring or aconventional helical spring (See FIGS. 117 and 118).

Moreover, with reference to FIG. 117, the piston subassembly 484 caninclude a platform 498, the position of which is adjustable by turning acentral screw shaft 500. Again, it is contemplated that the screw shaft500 be percutaneously accessed for ease of adjustment. Further, thedampening element can also involve a fluid-dampening system (FIGS. 117and 118). Holes 502 formed in an end of position 492 effect a slowmovement of fluid 504 through the assembly to prevent rapid changes invelocity.

Thus, the energy absorbing substructure 496 is engaged only at maximalcompression of the assembly and at all other times remains free withinthe device.

Turning now to FIGS. 119-127, further embodiments of structureincorporating features of the present invention are depicted. Inparticular, the energy manipulation assembly 510 shown in FIGS. 119 and120 includes first and second attachment structures 512, 514 havingcontours selected to match outer surfaces of body anatomy. An energyabsorbing member 516 includes a pair of spaced ends each being pivotablyattached to one attachment structure. The connection to the attachmentstructures 512, 514 as well as the energy absorption member 516 canfurther be sheathed in encasing structure 518 as described above. Inthis way, the overall structure assumes a low profile and generallyatraumatic assembly which tends to cooperate with body anatomy.

In yet another approach (See FIG. 121), an energy manipulation assembly520 of the present invention can incorporate into a first of a pair ofattachment structures 522, 524 for mounting to body anatomy, an energymanipulation subassembly 526. Here, the attachment structure 522includes a first end for mounting to body anatomy as well as amidsection employing a spring assembly 528 and a second end 530including a slotted and cam assembly for engaging the second attachmentstructure.

Other bilateral energy manipulation assemblies 532 incorporating springsubassemblies are shown in FIGS. 122 and 123. In each, pivotingstructure is employed to connect energy manipulation assemblies 534including springs 536 mounted about central rods 538, to body anatomyattachment structures 540. Again, in order to provide more atraumaticsurfaces for contacting body tissue, portions of these approaches can besheathed in encasing material 542. The manner in which such energymanipulation assemblies cooperate with the natural articulation of bodyjoints is shown in FIGS. 124 and 125.

FIGS. 126 and 127 depict an approach where the energy manipulationassembly 546 includes a first part 548 and a second part 550, the firstand second parts only engaging when the body anatomy approaches analigned configuration. In this way, energy manipulation is achieved intension but not in flexion.

Various further details of mounting or attachment structure are shown inFIGS. 128 and 129. Again, the present invention contemplates attachmentstructure 554 which follows the exterior contour of anatomy such asbones to which the attachment structure 554 is mounted. Moreover, suchattachment structure 554 can extend longitudinally varying distancesalong the body anatomy. Furthermore, the contemplated attachmentstructures 556 can extend a substantial lateral distance along bodyanatomy as well as longitudinally to define various geometries. In oneaspect, the attachment structures can assume a modified Y-shape.

With reference to FIG. 130, still yet a further embodiment of an energymanipulation assembly 560 incorporating various features of the presentinvention is shown. Configured between spaced attachment or body anatomystructures 562 is a complex energy absorption subassembly 564. Anadjustment mechanism 566 can be affixed to one attachment structure 562so that the degree of energy manipulation can be modified as needed. Inthe approach depicted, the adjustment mechanism 566 includes a slottedsection 568 that receives a screw 570 which can be manipulated to allowthe assembly to slide towards and away from the energy absorbing member564. The energy absorbing member further includes a rotating, arcuatearm 572 which alternatively engages the attachment structure 562 havingthe adjustment subassembly 566, and a spring or otherwise biasedprojection 574. The various geometries and dimensions of the componentsof this approach are selected to accomplish desired load manipulationcooperating with natural articulation of the body anatomy being treated.

By way of example, the energy manipulation assembly 612 depicted in FIG.131 could be employed to provide varying degrees of energy manipulationduring a gait cycle and patient healing. The energy manipulation member614 can include a spring 618 which slides within a slider 620 duringnormal motion. At first the spring 618 does not engage but at some pointafter implantation for example three weeks, a rotation tab 622 is lockedwithin a slot 624. At that point, the sliding spring engages the tab 622at key stages of gait and absorbs desired amounts of energy.

Turning to FIG. 132, yet a further contemplated embodiment is described.Here, an adjustable spring unit can be found within a base plate andjoint elements are contemplated to be part of a replaceable unit. Inthat regard, a dovetail mating section 627 as well as a ball and socketjoint 628 are placed between the energy manipulator 629 subassembly andone or more base assemblies 630.

Various different types of mounting screws are also contemplated to beused with this as well as other systems. Thus, there are at least twoforms of screws, namely, a large thread design for a cancellous screwand a finer thread intended for denser cortical bone. The threads areorientated at opposing angles (˜8 degrees) to anchor into a wedge ofbone making removal of the plate through pull out very difficult. Theheads of the screws are designed with the screw holes to ensure thecorrect trajectory of the screw. Installation of the screw will utilizea screw guide that initially locks into the screw hole on the platethereby defining the desired trajectory and the screw is screwed intothe bone through the screw guide which is then removed. Moreover,cortical screws can be angled as much forward toward an opposite cortexas possible without causing problems in the plate. The cancellous screwscan be angled in such a way so as to grab hold of as much bone aspossible.

As mentioned above, the present invention has applications to variousparts of the body. As shown in FIGS. 132 and 133, an energy manipulationassembly 630 can be placed within the cavity 632 between the acromiom634 and the humerus 636 bones. Although various approaches arecontemplated, in one aspect the energy manipulation assembly can includea spring loaded body 638 between fixation points 640. A bearing surface642 in the form of a ball bearing is further contemplated as is a springcompression adjustment subassembly 644.

In an application to the foot (See FIG. 134), an energy manipulationassembly 646 can be placed between the tibia 648 and the calcareous 650bones to address problems with the ankle. Such an approach can helpalleviate pain as well as address symptoms associated with a conditionreferred to as drop foot. Thus, the assembly 646 can be configured toaccomplish a lifting motion on the foot.

Applications to the hand and finger are also contemplated (FIGS. 135 and136). Here, one or more load manipulating assemblies 660 can bepositioned between distal 662 and middle 664 phalanges as well asbetween middle 664 and proximal 666 phalanges. Moreover, distractionunits 668 can be placed between adjacent phalanges 670 to treat variousconditions.

Moreover, the present invention has applications to the spine (See FIGS.137 and 138). Accordingly, a load sharing or energy manipulating device680 can be attached to and placed between vertebra 682 to off-load adisc 684. The energy manipulation device 680 can be attached to the sideof the vertebra 682 (FIG. 137) or can be affixed to facets (FIG. 138).Moreover, the device 680 (See FIG. 137) can include various of thepreviously described features such as adjustment nut 686 effecting theaction of a shock absorber spring 688. A load transfer unit 690 can befurther provided to include another spring 692 as well as adjustment nut694. A pair of fixating components 696 are further provided for mountedto body tissue.

It is to be borne in mind that each of the disclosed various structurescan be interchangeable with or substituted for other structures. Thus,aspects of each of the bending spring, cam engagement, segmented supportand piston support assemblies can be employed across approaches.Moreover, the various manners of engaging energy absorbing structurewith attachment structure and attachment structures to body anatomy canbe utilized in each approach. Also, one or more of the various disclosedassemblies can be placed near a treatment site and at various angleswith respect thereto. Pressure sensing and drug delivery approaches canalso be implemented in each of the various disclosed embodiments.

Certain components of most embodiments of the present invention aredesigned for easy removal and, if necessary replacement while others areintended for permanent fixation. The permanent components are fixationcomponents which have bony ingrowth promoting surfaces and areresponsible for fixation of the system to the skeletal structure. Theremovable components include the mobile elements of the system such asthe link members and/or the pivots or ball joints.

The advantages of this feature of the system include the ability toexchange key components of the system due to device failure, patientcondition change or newer improved systems being available. Additionallyif the patient subsequently requires further surgery the links may beremoved to facilitate the additional procedure.

Further, certain of the contemplated mechanisms can be made to becompletely disengaged mechanically and then brought into action undervarious conditions and during certain phases of the gait cycle. Thisdiscontinuous functionality—and the ability to tune that functionalityto a particular patient's gait or pain is consequently a feature of thepresent invention.

Location of the permanent fixation components is important to fixationstrength, ability to complete subsequent procedures, and location ofpivots or ball joints. The fixation strength of the system, andtherefore load bearing capacity, is dependent on the integrity of thebone onto which the component is fixed. To ensure strong fixation, inone embodiment, the fixation components span along the cortical bone andcancellous (or trabecular) bone. For example on the knee, the componentwould reside on the femoral shaft and extend down onto the trabecularbone on the end of the femur. Also, the system may utilize fixation ontwo cortical surfaces using through pins or bicortical screws.

A common joint procedure is joint replacement as previously described.The procedure of replacing a diseased joint includes resection of thesurfaces of the joint and replacement with synthetic materials. Toenable implantation of the energy absorbing system without impacting thepotential to complete subsequent procedures (e.g., joint replacement)the permanent fixation components in a preferred embodiment arepositioned at a location that does not compromise the total joint zone.

Many articulating joints are not simply pivot joints but involve complexmulti-axis rotation and translation movements. To achieve its intendedpurpose, the energy absorber must accommodate these movements but alsoabsorb and transfer energy during the required range of motion. To do sothe joints on the device may be either in case A located at points onthe bones of least motion, or in case B the joint mechanism mustincorporate motion beyond simple uni-axial rotation or a combination ofboth.

In the case of A, the fixation components are positioned such that theyorientate the attached device joint locations to preferred locationsdescribed by minimal or known motion characteristics. The device jointlocations may be finely adjusted within a defined region on the fixationcomponent to further optimize the device joint location. In the case ofB) the device joint mechanism accommodates the positional changes andtherefore can be placed on any distal point on the fixation component.

Therefore, the present invention provides a number of ways to treat bodytissues and in particular, to absorb energy or manipulate forces toreduce pain. The present invention can be used throughout the body buthave clear applications to articulating body structures such as joints.

Thus, it will be apparent from the foregoing that, while particularforms of the invention have been illustrated and described, variousmodifications can be made without parting from the spirit and scope ofthe invention.

What is claimed is:
 1. An implantable device for relieving knee jointpain while a patient is ambulating, the device comprising: a first baseand a second base each configured for attachment to bones on oppositesides of a patient's knee joint; and an energy manipulation assemblycomprising: a spring; a rod; a mating section engaged to the first base;a first joint positioned between and connected to the mating section andone of the rod and the spring; and a second joint positioned between theother of the rod and the spring and the second base, wherein the rod isconfigured to compress the spring and transfer load between the firstbase and the second base when the first base and the second base are afirst distance apart while a patient is ambulating, and the rod isconfigured to move relative to the spring while a patient is ambulatingsuch that the energy manipulation assembly transfers no force betweenthe first base and the second base beyond a point where the first baseand the second base are a second distance apart, wherein the seconddistance is larger than the first distance.
 2. The implantable device ofclaim 1, wherein at least one of the first joint and the second jointprovides multiple degrees of freedom.
 3. The implantable device of claim2, wherein at least one of the first joint and the second jointcomprises a ball and socket joint.
 4. The implantable device of claim 1,wherein one of the mating section and the first base comprises aprotrusion configured to engage a recess in the other of the matingsection and the first base.
 5. The implantable device of claim 1,wherein the energy manipulation assembly further comprises a secondmating section connected to the second joint and releasably engaged tothe second base.
 6. The implantable device of claim 5, wherein one ofthe second mating section and the second base comprises a protrusionconfigured to engage a recess in the other of the second mating sectionand the second base.